Process of tanning hides and pelts with the aid of iron compounds



Patented Aug. 16, 1938 UNITED STATES- PROCESS OF TANNING HIDES AND PELTS WITH THE AID OF IRON COIWPOUNDS Eugen Immendoerfer and Hermann Loewe, Ludwigshafen-on-the-Rhine, and Herbert Muench, Mannheim, Germany, assignors to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-onthe-Main, Germany No Drawing. Application June 18, 1936, Serial -No. 85,846. In Germany June 26, 1935 14 Claims.

The present invention relates to a process of tanning hides and pelts with the aid of iron compounds.

We have found that hides and pelts can be tanned in an excellent manner by employing tanning agents comprising soluble iron, and more particularly ferric compounds and polycarboxylic substances containing at least one double linkage in the molecule, i. e., the said acids themselves or their salts. The said tanning agents may consist of mixtures or of reaction products of iron compounds and the said polycarboxylic substances. As suitable polycarboxylic substances may be mentioned for example maleic acid, phthalic acid, mellitic acid and hemimellitic acid. Such dicarboxylic acids are especially suitable in the molecule of which the two carboxylic groups are attached to two adjacent carbon atoms joined by a double linkage. It is advantageous to employ acids which do not give intense colorations with iron salts. The iron compounds and the said polycarboxylic substances may be first brought together and the products thus obtained used for tanning, or the single components may be allowed to act in any sequence on the materials to be tanned. The tanning process may also be combined with any other tanning methods, as for example those which make use of vegetable, synthetic or mineral tanning agents.

Leather andskins tanned with the aid of the said tanning agents are distinguished by very good plumpness. They have an excellent sta-. bility in storage and are generally speaking only slightly colored.

The following examples will further illustrate the nature of this invention but the invention is not restricted to these examples. The parts are by weight.

Example 1 1480 parts of phthalic anhydride are dissolved in 800 parts of caustic soda, the whole is diluted to 12,000 parts and a solution of 510 parts of anhydrous ferric chloride in 5000 parts of water is slowly added while stirring. 5000 partsb-funpickled unhaired calf pelts are introduced into the solution and fulled until fully and thoroughly tanned. The leather is rinsed well, fatted with a train oil emulsion and finished as chrome leather. A leather is obtained having beautiful plumpness, smooth grain and rather pale color.

The unhaired calf pelts, before they are subjected to the said treatment, may also be pretreated with a solution which contains 1 part of ferric chloride and 10 parts of common salt to each parts of Water.

Example 2 Pickled unhaired calf pelts are drummed with a solution of 15 per cent of maleic acid, 18 per cent of ferric nitrate and 7.5 per cent of calcined sodium carbonate in percent of water, the percentages being with reference to the weight of unhaired pelts. Pulling is continued until the section is thoroughly colored and then a. solution of 2.2 per cent of calcined sodium carbonate is added in small batches during the course of two days.

The leather is left overnight on the trestle and is then treated for 4 hours with 3 per cent of the sodium salt of the condensation product from naphthalene sulphonic acid and formaldehyde prepared according to the U. S. Patent 1,336,759 in 100 per cent of water and then rinsed, until the section shows a pH value of 5. The leather is then fatted with a sulphonated train oil and finished off in the usual manner.

Example 3 Example 4 35 Pickled unhaired calf pelts are drummed with a solution of 9 per cent of ferric sulphate and 1 per cent of sodium phthalate in 100 per cent of water (the percentages being calculated on the weight of the pelts) until the'section of the pelt is uniformly colored throughout. In the course of about 24 hours 4 per cent of sodium phthalate are added in the form of a 3 per cent solution. 2.2 per cent of calcined sodium carbonate are then slowly added in the'form of a 5 per cent solution. The pelts are further treated as described in Example 2.

, a solution of 9 per cent ofiferric sulphate and 1 per cent of a mixture consisting of 69 parts of sodium phthalate and 31 parts of calcined sodium carbonate in 100 per cent of water (the percentages being calculated on the weight of the pelts) until the section is colored throughout.

Another 6.2 per cent of the sodium phthalatesodium carbonate mixture mentioned are then added slowly in the form of a 3 per cent solution. The pelts are further treated as described in Example 2.

What we claim is 1. The process of tanning hides and pelts, which comprises treating them with a tanning agent comprising an iron compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

2. The process of tanning hides and pelts, which comprises treating them with a tanning agent comprising a mixture of a soluble ferric compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

3. The process of tanning hides and pelts, which comprises treating them with a tanning agent comprising a. reaction product of an iron compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

4. The process of tanning hides and pelts,

which comprises treating them with a tanning agent comprising a mixture of an iron compound and an aromatic polycarboxylic substance.

5. The process of tanning hides and pelts, which comprises treating them with a tanning agent comprising an iron compound and an aromatic dicarboxylic substance.

6. The process of tanning hides and pelts, which comprises treating them with a tanning agent comprising a ferric salt and a phthalic acid substance.

7. Tanning agents comprising an iron compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

8. Tanning agents comprising a mixture of a soluble ferric compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

9. Tanning agents comprising a reaction product of an iron compound and a polycarboxylic substance containing at least one double linkage between the carbon atoms in the molecule.

10. Tanning agents comprising a mixture of an iron compound and an aromatic polycarboxylic substance.

11. Tanning agents comprising an iron compound and an aromatic dicarboxylic substance.

12. Tanning agents comprising a ferric salt and a phthalic acid substance.

13. Tanning agents comprising a ferric salt and a maleic acid substance.

14. Tanning agents comprising a ferric salt and a mellitic acid substance.

EUGEN IMMENDOERFER. HERMANN LOEWE. HERBERT MUENCH. 

